1. Field of the Invention
The present invention relates to the production of circuitized layers and multi-layer ceramic laminates for electronic application, and more particularly to the production of laminates from a plurality of dielectric ceramic greensheets patterned with conductive circuit layers interconnected by conductive vias to form multilayer sub-laminate units.
The increasing demands for miniaturization and greater electrical capacity of electronic components has created production and performance problems. For example, miniaturization requires the use of thinner insulating ceramic greensheet layers, finer-line printed circuit conductive layers and smaller, more precise vias or holes through each greensheet layer to receive conductive paste and connect predetermined fine-line circuitry of the patterned conductive layers spaced by the insulating greensheet layers.
Thin greensheet layers, less than about 3 mils in thickness, are difficult to process into multi-layer ceramic laminates in the conventional production process because the thin greensheets distort greatly and lose mechanical strength during normal processing, particularly during screening with conductive paste composition, and weakened, distorted or warped greensheets cannot be laminated into electrically-continuous packages.
2. Background Art
It is known to produce multi-layer ceramic laminates and composites thereof for electronic applications, and reference is made to U.S. Pat. Nos. 4,349,862; 4,799,984; 4,894,258; 4,929,295; 5,089,455 and 5,232,765. U.S. Pat. No. 5,232,765 prevents or reduces distortion or shrinkage of the greensheet ceramic layers by maintaining pressure on the laminates during firing. U.S. Pat. No. 4,799,984 employs a rigid substrate as a support for the build-up of pre-punched greensheet layers and conductive layers during the production of multi-layer ceramic laminates. The substrate is retained in the process of U.S. Pat. No. 4,799,984 to become an integral part of the formed MLC. In typical prior-known processes, the individual greensheets are each screened prior to stacking and lamination.